Apparatus for producing nonwoven fleeces



Sept. 15, 1970 HARTMANN APPARATUS FOR PRODUCING NONWOVEN FLEECES FiledNov. 7, 1966 INVENTOR LUDWIG HARTMANN BY @w.

ATTORNEYS. 6

United States Patent 3,528,129 APPARATUS FOR PRODUCING NONWOVEN FLEECESLudwig Hartmann, Oberflockenbach, Germany, assignor to Carl FreudenbergKommanditgesellschaft, Weinheim, Bergstrasse, Germany, a corporation ofGermany Continuation-impart of application Ser. No. 495,929, Oct. 14,1965. This application Nov. 7, 1966, Ser. No. 592,545 Claims priority,application Germany, Oct. 24, 1964, 1,435,466; Nov. 11, 1965, 1,660,297Int. Cl. B28b 21/54 US. Cl. 18-8 2 Claims ABSTRACT OF THE DISCLOSUREApparatus for producing a nonwoven fabric having filaments ofnoncircular cross section by melt spinning filament-forming materialthrough spinneret holes having noncircular cross-sections, whichfilament holes are linearly aligned to form at least one row of meltspun filaments, the axes of which are substantially parallel,air-drawing all of these filaments substantially simultaneously directlyout of the spinneret holes, passing these filaments and the drawn airthrough channel means, and then laying down these drawn filaments on asuit able substrate While still in the tacky condition, whereby to causethese filaments to bond together predominantly at their crossing points.

The present invention relates to apparatus for the manufacture oftextile fiber products from a fused mass of fiber-forming high polymersand has as an object the manufacture of nonwoven textile products ofsubstantially improved properties.

This application is a continuation-in-part of application Ser. No.495,929, filed Oct. 14, 1965, now abandoned.

In the fusion spinning process for the manufacture of fibers, spinneretsare generally used which have concentric circles of holes. (See Hill,Fasern aus Synthetischen Polymeren, 1956, pp. 378 et seq.) The fiberswhich Hill discloses are introduced, at a distance from the spinneret,into a passageway into which air currents of certain temperature andhumidity are injected at low velocity contrary to the direction ofmovement or crosswise thereto. (See also German Pat. 916,458, drawings.)These endless fibers are then brought together in' the manner of a cableor string, and the string is wound into a roll. In U.S. Pat. 3,117,055,it is proposed, for the manufacture of nonwoven fleeces, not to wind thefilaments, but to guide the filaments together at a distance from thespinneret, accelerate them with air by means of an annular jet, and alsocharge them electrically. See FIG. 1 of US. 3,117,055. The chargingcauses the fibers as they fall to a fleece form, to repel one another,and separate for collection in random array on the form. It hasdeveloped, however, that it is difficult to effect suitable separationfor the production of thin sheets with a uniform structure.

It has furthermore been proposed, for the manufacture of filtermaterial, to extrude plastic masses from fiat nozzles having adjacentslots. The nozzles are formed of two Wedges compressed together, whichcontain grooves running lengthwise, which when passed together, form asort of row of holes (Wente, Ind. and Eng. Chemistry, vol. 48, p. 8,August 1956). On each side of the row of holes there is located an airslit parallel therewith, from which air currents are driven. The aircurrents seize the extruded fibrous masses and carry them forward. It

3,528,129 Patented Sept. 15,, 1970 has not been possible by this processto produce fiber batts of high strength, because due to the excessiveturbulence of the air currents, especially when they combine with theoutside air, it is not possible to achieve a high orientation of thechain molecules within the fibers. Furthermore, the nozzle wedges do notfit together in a suitable manner to permit uniform fiber formation overrelatively large production widths.

As is disclosed in application Ser. No. 341,489, filed Jan. 27, 1964, ithas now been found that these diificulties can be overcome by extrudingspinnable melts from nozzles which contain the spinning holes in theform of a straight row (see FIG. 1a hereof) and by guiding the rank ofendless fibers emerging from the row by means of air currents within afilament drawing passageway in such a manner that they remain separatefrom one another up to the moment when they are collected on a screenbelt (see FIG. 2), or other fleece forming support.

It has now been found that improved results can be obtained if thespinneret head holes are nonround in cross-section, especially if theholes have a branched cross-section. Desirably, the fused polymer massissuing in a filament form from the nonround holes is drawn into afilament and cooled to provide the filament in solid state wherein thesolid filament retains impressions corresponding to the branchedcross-section. The drawing can be by means of air currents as isdescribed in said Ser. No. 341,489. The filaments are collected asmono-filaments on a fleece form. The nonround monofilaments arecharacterized in that they have improved adhesion for binders.Accordingly, the invention particularly contemplates that a binder willbe applied to the randomly arrayed mono-filaments collected on thefleece form.

It has also been found that the nonround filament form issuing from thespinneret can readily be formed into a crimped fiber. This is done byutilizing gas streams to elongate the filament form issuing from thespinneret. Variation in the influence of the gas stream on differentportions about the circumference of the filaments affects the crimping.Crimping is further facilitated by utilization of gas streams ofdifferent temperature.

The invention is further described in reference to the accompanyingdrawing, wherein:

FIG. 1 is a perspective view of a spinneret head according to theinvention;

FIG. 2 is a perspective view of apparatus for forming a fleece by themethod of the invention; and

FIG. 3 is a cross-sectional view of a filament immediately followingissuance from a spinneret hole as is shown for the spinneret head inFIG. 1, and after cooling of the same filament to the solid state.

The spinneret 1 is outfitted with a spinneret head 2 having a pluralityof spinneret holes 3 for receiving molten filament forming material fromthe spinneret and issuing it in a plurality of molten filament forms.The holes 3 are nonround in cross-section, and preferably are branched,for example, T-shaped, or Y-shaped, as is shown in FIG. 1. Elongated airoutlet passageways 4 are positioned on either side of the row ofspinneret holes 3. Also, a guide passageway 5 is disposed to receivefilament forms issuing from the spinneret and to guide them in parallelrelation to the screen 6 which serves as a fleece form. Air passageways7 are provided in the guide passageways, for the introduction of airinto the guide passageways to assist in the treatment of the filamentforms. A plurality of spinnerets and guide passageways can be utilized.The apparatus involving the combination of spinnerets, guidepassageways, and fleece collecting form is more fully described in saidSer. No. 341,489. The fleece form 6 re- 3 ceives the filaments from thefilament form 5 and collects the filaments disposed on the form inrandom crossing relation to form a felted fleece 8.

The apparatus and the method of the invention are particularly effectivewhen the spinneret head is of the type shown in FIG. 1, wherein the headis elongated and the spinneret head holes are disposed along a lineextending longitudinally of the head, while at the same time the headincludes the gas passageways 4 for directing streams of gas along thepath of the filament forms issuing from the holes 3.

The cross-section of the filament forms issuing from the spinneret holes3 is as shown in FIG. 3.

Any suitable binder can be applied to the fleece 8 on the form 6 via thespray conduit 9. The binder can then be distributed through the fiee'ceby the calender rolls 10.

It will be observed that the outlet opening of the air passageways 4 areasymmetrical with respect to the outlet openings of the holes 3. Thisfacilitates crimp1ng. The spinnerets here used preferably have thesplnmng orifices spaced very close together (1.5 to 2 mm. apart).Furthermore, they are all shaped very uniformly, and the spinningorifices are parallel and equal to one another, so as to assure that theendless fibers, after they emerge from the spinning orifices, do nottouch one another for a distance of at least 500 mm. or even more, andremain on parallel courses. Now, it is important that a filament drawingpassageway 5 be associated with each row of spinning orifices, and thatpairs of high velocity air jets are directed into the passageway in thedirection of the flight of the fibers, in such a manner that the endlessranks of fibers emerging from the spinnerets are struck on both sides byjets of air from slits (a-l and a2, through passageways 4, and b-l andl2-2, through passageways 7). 1n the embodiment shown in FIG. 2, twopairs of air jets are represented, pair a1-a2 directly at the spinneret,and pair b-1-b-2 at a distance therefrom in the drawing passageway. Toincrease the draft of the fibers and hence the strength of the fiberbatts, additional pairs of air jets can also be used. To obtain otherfiber properties, e.g., to achieve a shorter elongation, the first pairof air jets, (1-1 and a-Z, can be very greatly throttled in comparisonwith 11-1 and 17-2, and in the extreme case, it can be shut off. 'Inorder to demonstrate the influence of the drawing passageways,experiments were performed first without drawing passageways and withair jets a-l and a2 alone, and then with drawing passageways and withthe addition of air jets b-l and b2, at increasing velocities. Theresults obtained are shown by the following table:

Substance spun: Nylon 6 Throughput: 0.1 g. per spinning orifice It isapparent that, by arranging the conditions appropriately, e.g., drawingpassageway operated at high air velocity, high strengths are obtained inthe fibers and hence in the batting made therewith. It is furthermoreapparent that the ultimate tensile strength, which to some extentreflects the molecular orientation, can be varied over a very widerange.

Another considerable possibility of variation in the process is providedby variation of the temperatures of the air jets. For example, 11-1 anda-2 can have a higher temperature than b-1 and 11-2, or the temperaturemay be equal. If the temperature of jets 11-1 and [1-2 are increased, itis possible to sustain the plasticity of the endless filaments coming inthe melted state from the spinneret and thus achieve an improvement inproperties, depending upon the end product. An especially advantageouseffect is achieved when the temperatures of the individual jets of apair are different, i.e., a-l different from a-2 or b-1 different fromb2. In this manner it is possible, for example, in the case of abranched crosssection, e. g., Y-shaped cross-section, in the spinningorifice, to produce a tension variation within the fiber, since the airjets both stretch the fibers and cool them, and thus create differentorientation conditions about the circumference of the fibers. It hasdeveloped that improved crimping can be produced within the fibers inthis manner, and that this crimping has a very great effect on theproperties of the fiber batts that are formed from them. It makes thefiber batts bulkier and gives them a softer feel. Further, the Y-shapedor branched cross-section of the filaments improves the adhesion of thefibers for binding substances, which can be any suitable bindingsubstance.

The ranks of endless fibers emerging from the drawing passageways arecaught on a screen felt having an aspirating means beneath it similar tothe indication in FIG. 2 of Ser. No. 341,489. The screen belt canfurthermore be arranged either athiwart the row of spinning orifices (asrepresented) or in line therewith, or at any desired angle thereto,depending on the end products desired. The high uniformity of the fiberbatt is achieved by the fact that the individual fibers, from the momentof their formation to their deposition on the form, remain substantiallyunaffected by the other fibers, and primarily by the fact that they arenot brought together in the manner of a cable or string. The high degreeof mutual entanglement is achieved by the fact that the spinningorifices are very close to one another (e.g., 2 mm. apart), and thespinning speed is several times greater than the belt speed. Forexample, a spinning speed of about 2000 m./min. is used with a screenbelt speed of about 20 m./min. Now, since the spacing of the spinningorifice is very small in comparison with the diameter of the fiber loopsthat form and are deposited on the screen belt, a mutual felting occurs.This can be effected by rocking the drawing passageways as disclosed inSer. No. 341,489. The entanglement of the fibers is further augmented bythe use of the branched, e.g., Y-shaped cross-section, and in the casein which an increase in crimping is produced by air jets of differenttemperature.

EXAMPLE 1 Polycaprolactam granules (reduced viscosity-2.28) were meltedin a worm press and fed to a spinning pump at a temperature of 260 C.The spinning pump proportioned the melt to a spinneret heated to 228 C.The spinneret consisted of a rectilinear row of spinning orifices, theseorifices being Y-shaped and spaced 2 mm. apart. An air slit 0.3 mm. widewas disposed on each side of the row of orifices, at a distance of 0.4mm. Air currents at 230 C. were ejected from both air slits at apressure of 0.1 atmosphere overpressure. These paired air streams seizedthe row of filaments emerging from the Y-shaped cross-sections andcarried them forward. The filaments along with the air streamsenveloping them on both sides were introduced into an air passageway 5which had been mounted at a distance of 40 mm. from the nozzle (FIG. 2The distance between the plates of the rectangular air passageway was 20mm. At the entry of the air passageway there was arranged another pairof air slits 7, as shown in FIG. 2, from which air at room temperaturewas ejected at 1.5 cu. m. per minute. The second pair of air jetsproduced an additional pulling effect on the rank of filaments, so thatan additional force was exerted and took effect in the zone where thedrawing was being done. Furthermore, these air streams produced acooling of the filaments and a freezing of the molecular orientationobtained. As a result of the guiding passageway surrounding the rank offilaments on all sides, turbulence was prevented, so that the filamentsremained on a parallel course and did not entangle or come together intocables. At the bottom end of the 40-centimeter-long guiding passage 5,the air velocity was 1500 meters per minute.

The filaments were built into a coherent batting by aspiration. They hada titre of 0.81 denier, a tensile strength of 4 grams per denier and anelongation at rupture of 140%. The filament cross-section was triangularwith indented sides, i.e., retained impressions corresponding to theshape of the branched spinneret holes, and the fibers were highlycrimped.

EXAMPLE 2 Example 1 is repeated with the modification that the airtemperature of the air issuing from one of the passageways 4 is 230" C.,while the air temperature of the air issuing from the other of thepassageways is 150 0., and the air temperature of the air issuing fromone of the air passageways 7 is room temperature, while the temperatureof the air issuing from the other of the passageways 7 is 75 C. Morecrimping of the fibers is obtained due to this variation.

Suitable binders are disclosed in Nottebohm, Pat. 2,719,806, Oct. 4,1955.

By crimping is meant that the fibers are distorted so that when disposedlongitudinally, with no tension applied thereto, the application oftension will initially effect an elongation, without any correspondingreduction in cross-section.

While good results are obtained by practicing the process of thisinvention in the apparatus hereof, it has been found that under somespinning and drawing conditions, the filaments are not treated exactlyuniformly with respect to all surfaces thereof. Under some conditions,the resultant fiber nonuniformities produce a nonuniform crimping of theindividual fibers. This in itself is not too bad since the fibers areintended for use in a relatively random nonwoven fibrous batt or fleece.

However, it has been found that, if all of the fibers are spun fromnoncircular spinning nozzles which are parallelly oriented, theresulting fibers may cool nonuniformly, but similarly, and thus thenonwoven fabric may have an overall slant pattern as opposed to therandom array of fibers which is usually desired. It has been found thatthis overall slant pattern of the resultant fabric can be simply avoidedby spinning the noncircular filaments from spinning nozzles which arerandomly oriented with respect to each other. In this way, thepotentially irregular cooling and crimping will not uniformly affect allfilaments and there will again be produced a random oriented fleeceproduct. In this regard, it is preferred that every other spinningnozzle be oriented at 180 degrees from its adjacent nozzles. Forexample, every other Y-nozzle will be upside down with respect to itsadjacent nozzles.

While the invention has been described with respect to particularembodiments thereof, these embodiments are merely representative and donot serve to set forth the limits of the invention.

What is claimed is:

1. In an apparatus for the continuous production of substantiallyendless filament nonwoven fabrics which comprises spinneret means havingat least one substan tially linearly aligned row of spinning nozzles,gas Outlet means adjacent to and on opposite sides of said row ofspinning nozzles for impinging a gas stream onto two opposite sides ofthe rank of filaments spun from said row of nozzles; channel meansadjacent to and spaced longitudinally from said spinneret and from saidgas opening means adapted to be associated with (a) said single row ofsubstantially endless filaments and adapted to receive said filamentsand at least a portion of said gas stream therein and to pass suchtherethrough, said channel means having an inlet substantially alignedwith, adjacent to, and spaced from said spinning nozzles and from saidgas outlet means; and continuously moving fleece-form filament receivingmeans spaced from the end of said channel means opposite to the endthereof adjacent to said spinneret and disposed at an angle to saidfilaments adapted to receive said substantially endless filaments uponemergence thereof from said channels; the improvement which comprisessaid spinning nozzles being Y-shaped and adjacent nozzles are positionedout of phase with each other.

2. In an apparatus for the continuous production of substantiallyendless filament nonwoven fabrics which comprises spinneret means havingat least one substantially linearly aligned row of spinning nozzles, gasoutlet means adjacent to and on opposite sides of said opposite sides ofsaid row of spinning nozzles for impinging a gas stream onto twoopposite sides of the rank of filaments spun from said row of nozzles;channel means adjacent to and spaced longitudinally from said spinneretand from said gas opening means adapted to be associated with (a) saidsingle row of substantially endless filaments and adapted to receivesaid filaments and at least a portion of said gas stream therein and topass such therethrough, said channel means having an inlet substantiallyaligned with, adjacent to, and spaced from said spinning nozzles andfrom said gas outlet means; and continuously moving fleece-form filamentreceiving means spaced from the end of said channel means opposite tothe end thereof adjacent to said spinneret and disposed at an angle tosaid filaments adapted to receive said substantially endless filamentsupon emergence thereof from said channels; the improvement whichcomprises said spinning nozzles each having cross-sections which aresubstantially the same and wherein said nozzles are randomly orientedwith respect to each other.

References Cited UNITED STATES PATENTS 2,121,802 6/1938 [Kleist et al.2,331,945 10/ 1943 Pazsiczky et al. 2,411,660 11/1946 Manning. 2,437,2633/1948 Manning. 2,604,667 7/1952 Hebler 264-68 2,644,779 7/ 1953Manning. 3,028,623 4/ 1962 Labino 18-2.5 3,154,836 11/1964 Hoag et al.3,219,739 11/1965 Breen et al. 214168 3,297,807 1/ 1967 Settele.3,303,169 2/1967 Pitzl 161-172 X 3,366,722 1/1968 Tessier. 2,508,4625/1950 Marshall 18--8 3,266,969 8/1966 Makansi. 3,379,811 4/ 1968Hartmann et al.

FOREIGN PATENTS 296,015 5/ 1965 Netherlands.

JULIUS FROME, Primary Examiner I. H. WOO, Assistant Examiner U.S. Cl.X.R.

